docs: def send(subject, recipients, template_base, **kwargs):
      '''
      Send a given email to multiple recipients.
  
      User prefered language is taken in account.
      To translate the subject in the right language, you should ugettext_lazy
      '''
      sender = kwargs.pop('sender', None)
      if not isinstance(recipients, (list, tuple)):
          recipients = [recipients]
  
      debug = current_app.config.get('DEBUG', False)
      send_mail = current_app.config.get('SEND_MAIL', not debug)
      connection = send_mail and mail.connect or dummyconnection
  
      with connection() as conn:
          for recipient in recipients:
              lang = i18n._default_lang(recipient)
              with i18n.language(lang):
                  log.debug(
                      'Sending mail "%s" to recipient "%s"', subject, recipient)
                  msg = Message(subject, sender=sender,
                                recipients=[recipient.email])
                  msg.body = theme.render(
                      'mail/{0}.txt'.format(template_base), subject=subject,
                      sender=sender, recipient=recipient, **kwargs)
                  msg.html = theme.render(
                      'mail/{0}.html'.format(template_base), subject=subject,
                      sender=sender, recipient=recipient, **kwargs)
                  conn.send(msg)